Musings from the workshop
23rd March 15
Roman Blind Headrail Allowance Explained

What is headrail allowance?

Headrail allowance is the extra length we allow in the top section of the blind to cover the batten/rail and give room for the rod pockets, rings and eyelets on a wooden batten when the blind is pulled up. In our tutorials we suggest an absolute minimum headrail allowance of:

Traditional batten: HEADRAIL ALLOWANCE = Batten face + 3.5cm
Headrail mechanisim: HEADRAIL ALLOWANCE = Headrail depth + 2.5cm

The traditional wooden batten on the left has a face depth of 3cm and the minimum distance needed below the blind is 3.5cm. Note if you are using larger eyelets you may need more than 3.5cm below the batten. That gives an absolute minimum headrail allowance of 6.5cm.

The headrail on the right has a depth of 3cm and the minimum distance needed below the blind is 2.5cm, giving an absolute minimum headrail allowance of 5.5cm.

(Note the stitch line of the rod pocket marks the top of the blind fold.)

In this next example the headrail depth is 4cm and you can see the minimum needed below the headrail is 2.5cm, giving an absolute minimum headrail allowance of 6.5cm.

What if I make my headrail allowance to short?

The headrail allowance has to be sufficiently long to cover the face of the batten and allow room for the pleats to pull up so the blind can be pulled fully up.

If you do not allow enough headrail allowance the blind will not fully pull up. You can see here the headrail allowance used is too short because even though the rings are pulled up tight to the headrail the blind is still hanging down slightly.

What if I use a headrail allowance longer than the minimum?

If you use a headrail allowance longer than the minimum the blind will still work fine. Indeed we don’t usually use the absolute minimum, finding it is better to not be up against the limit. You can see the rings just hang slightly lower when the blind is up with the pleats aligned.

Extra Help & Comments

Sew Helpful
Post your questions and comments here, we will reply so everyone can see the answer.
Rachel
HI, can you let me know what brand of mechanism you use please? Thanks
Sew Helpful
The wholesale company we use to supply our blind rails haverecently  had some quality control issues with their gears being too stiff so we are in the process of sourcing a different supplier. So we can't recommend anyone at the moment.
Eleni
Hi, I am going to make roman blinds for most the windows of my house with a block out fabric without any lining. My fabric has no pattern and my concern is how the sewing lines will look. There will be one sewing line all around the blind and one for each roman blind tape for the dowels. What do you think? Any advice?
Sew Helpful
We don't make them like that. So really it is down to what you will be happy with. Be aware every stitch you make into the blackout will create a pinprick of light.
Sara
Can I use a 16mm aliminium rod for the headrail
Sew Helpful
I'm not sure what you are asking?. The Roman blind tutorials on the website show you how to make a wooden headrail in STEP 10 that requires eyelets and the velcro to be attached to it, otherwise the metal headrails usually come made up.

Can you expand what you mean by the question.
Doreen
If I staggered the depth of the folds to give a flatter look when in the up position, would that cause a problem? I realise the rings would all be at the same height and the overall depth of the pulled up blind would be increased but would it look better?
Sew Helpful
That is a cascade blind, whether it looks better or not is a design decision and dependant on what look you are trying to achive.
Anne
I am going to use tape with built in loops for the blind cord do I still need 2.5 cm plus the batten allowance?
Sew Helpful
We would still include a minimum 2.5cm extra with a headrail and 3.5cm with a wooden batten. Some of the extra space needed under the batten/rail is for the rod pocket (which will be in the tape), eyelets on a wooden batten and although you may choose not to use rings or breakouts on your tape the fabric loops will pull up away from the tape under tension requiring extra room.

Even with tape we would still use no less than the minimum values for the headrail allowance we have given here (you can always use more).

Note the figure of 2.5cm comes up later again in the tutorial, You will not need the 2.5cm of lining per rod pocket when calculating the amount of lining you need in STEP 4 of the tutorial. There is information about using tape in red on the tutorial page click on it to see more. 
Rebecca
This is just what I have been looking for, thank you so much for such a clear explanation.
Soular
The fabric I am making my blind out of has a pale background. Can I make the blind so that the rods can be taken out (so I can wash it) or is my only option to use tape rather than sew pockets into the lining. It needs to be sturdy as its in the boys bathroom!!
Sew Helpful
We NEVER wash blinds so we sew the rod ends  in. The fabric and lining will almost certainly shrink at different rates and it will never be the same again.
Pat Houghton
I'm a little confused by the picture you show when the blind is fully open as I would expect the pleats to be showing from the front, do I need different measurements if I want to do it that way?
Sew Helpful
To have the pleats staggered and showing in the up position, you would set the rod spacing out so they cascade.  See the Cascading blind calculator on the website.

In the example above the blind is a standard folds blind where the pleats all pull up in line. Again there is a blind calculator for standard folds on the website.

The only difference between the 2 blinds is the rod pocket positions.
robert price
Re roman blind with a drop of 160cms as an exact fit.

When raised, what is the drop measurement or is that controlled by the amount of folds in the blind.? My aim is to have less rather than more window covered when blind is raised.
Sew Helpful
The depth when pulled up depend on how many folds (pleat section you choose and the headrail allowance you use.

see our FREE calculator on the website, or STEP 2 of a roman blind tutorial on the site for more information.
Anita
I am making 2 blinds for windows that are close to each other but the windows are slightly different lengths. How best should I calculate the pleats. One window is127cm long and the other is 112cm long
Sew Helpful
Try and make them the same depth when pulled up. You can vary the heading allowance if required to achieve this.
Gillie
I am new to this, but have bought your video and hope to make 2 wide interlined blinds..I have measured the (Merrick & Day Rotary chain Roman blind) headrail allowance which seems much deeper than your examples - from the top of the rail to the bottom of the plastic chain mechanism (which is part of the headrail), it is 9cm - and then you suggest adding another 2.5cm. Does that sound right?
Sew Helpful
We are not saying add 2.5cm, we are saying adding 2.5cm is the absolute minimum to add as the blind will not lift up fully if you dont. You can always add more than 2.5cm (adding more will ensure the blind doesnt pull up short). 

9.5cm sounds quite deep for your headrail depth, your rail may have an unusual bracket at the end that protrudes deeper than the rail face. Look at the top pictures, showing the headrail face on (3cm) that is the depth you need to measure, because the bottom of the rail face is where the cords pull up to.

The blind works fine with a big headrail allowance, it just means it will cover more window when pulled up. Some people were trying to get their blinds so small when pulled up, they were not using enough headrail allowance and hence they were not pulling up fully when made. That is why we wrote this article to try and explain it.
Nicola rotchell
Hi, I have made several blinds but never found a formula for allowing the bottom of the blind with the flat baton in to show ..as a decorative feature e.g if fringing or contrasting ribbon is sewn on the bottom of the blind I would like it to hang a little lower rather than fully line up behind the other pleats?
Sew Helpful
The easiest way is probably to use the cascading blind calculator on the website. Set the cascade depth to 0cm (that would make all the folds be in line when pulled up) but set the bottom flap depth to the amount you want the bottom to show eg 3cm  (that would make the bottom flap hang 3cm below the line of the other pleats when pulled up).


Pooja
Hi, my blinds size is 224cm and I want headrail allowance is 28 cm and my pleat size is 15.9cm and 6 rods but when I pull my cords my blinds top pleat is bigger then the others so I can’t pull the cords till end, i have to stop my cords before. My question is how can I use stoppers or how can I stop my cords??
Sew Helpful
You need to stop pulling when they are inline.

If you put a stopper on the cord it will not travel through the rings so the blind wont work. 
Olivia West
Hi , firstly- I find your website so helpful! Please can you tell the measurements for your wooden batton that you use and would suggest? Many thanks!
Sew Helpful
We don't use them and recommend them anymore as the solutions to comply with current child safety regs are not robust, Before the child safety regs we used to use 18mm x 34mm battens.

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